The output beam of a Free Electron Laser (FEL) is typically emitted from the end of a wiggler (also called an undulator) in a narrow cone (see FIG. 1) which diffracts slowly and is initially travelling along the same line as the electron beam that produced it. If this radiation is to be used, the electron beam is separated from the optical power beam by means of a bending magnet. One consequence of this bending is that is in addition to the presence of the FEL photons, output radiation is produced by means of collective synchrotron emission at wavelengths longer than the electron pulse length (see FIGS. 2, 3, and 4). Also radiation known as edge radiation is produced at the transitions of the electron beam into and out of the bending magnetic field. These additional photon sources may be of high power and are generally undesirable as they may interfere with the use of the FEL output by giving incorrect signals on detectors, heating mirrors or otherwise negatively impacting the planned use of the FEL output. Accordingly, there is a need for an FEL system that produces an output radiation with reduced amounts of emission at wavelengths longer than the electron pulse length and reduced amounts of edge radiation.